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“One of the most influential biases in the acquisition of evidence is choice of the question, and the best evidence in answer to the wrong question is useless.”
Menticoglou & Hall 2002
Making the rounds on the internet is a new study finding that lying down during the pushing phase of labor results in more spontaneous vaginal births in first-time mothers with epidurals. That sounds like useful information, but let’s look closer.
Conducted in the U.K., the investigators randomly allocated 3,093 first-time mothers, who were at ≥ 37 weeks gestation with one, head-down baby and who had reached full dilation with a low-dose epidural, to either maintaining an upright position (walking, standing, supported kneeling, sitting, etc.) or lying on their side for as much of second stage (the time from full dilation to the birth of the baby) as possible. Women assigned to the upright group were free to lie down and vice versa, but most spent most of the time in the position to which they were assigned.
Already we have a problem: the study’s title and all the articles reporting on it have only said “lying down,” which would lead people to think that it includes lying on the back. Lying on the back and side-lying aren’t physiologically equivalent. Lying on the back puts the weight of the uterus and baby on the major blood vessels serving the uterus, which could lead to fetal distress. It also prevents the sacrum from flexing open to widen the pelvic passage, which could make it more difficult for the baby to pass through.
We have, however, bigger fish to fry. Among women assigned to lie down, 41% birthed under their own steam compared with 35% of women assigned to upright positions, or 6 more women per 100 having spontaneous births in the side-lying group. Statistical calculation showed that this difference was unlikely to be due to chance, and the investigators duly reported this as their main finding. Step back and look at the big picture, though, and their trial showed that among first-time mothers with an epidural who reached second stage, 59% to 65% had instrumental or surgical deliveries—and that’s not counting that some percentage of women were ineligible for the trial because they didn’t make it to second stage! Among women having a non-spontaneous delivery, 51% vs.55% had an instrumental vaginal delivery and 8% vs. 10% had a cesarean, which means they and their babies were exposed to the potential harms of those procedures. The investigators report other outcomes that give us an idea of what these might be: Among women, 6-7% sustained tears into or through the anal sphincter, and 3-4% required blood transfusion. Among babies, 12-13% required resuscitation at birth, 6-7% were admitted to a special care nursery, 22-23% didn’t have skin-to-skin contact in the 1st hour after birth, and 48-49% didn’t have breastfeeding initiated in the first hour.
Investigators should have been asking: “What’s wrong with this picture?” They can’t even claim they didn’t know their results were concerning. They had used a 55% spontaneous birth rate reported in another study to calculate how many women they needed in their trial to have a reasonable chance of detecting a difference between groups (power calculation). In the pilot phase, they realized that their study was only achieving a 34% spontaneous birth rate. A 55% spontaneous birth rate is no great shakes in my opinion, but it’s a darned sight better than 34%. Instead of acting as a wake-up call, though, the investigators merely considered whether they needed to recruit more participants, determined that they didn’t, and forged ahead, ignoring the broader implications. Blinders fully in place, the investigators contented themselves with presenting the results of a carefully designed, well-conducted trial that couldn’t see the forest for the trees.
The Take-Away: First-time mothers may wish to consider carefully whether they want to plan on having an epidural. In fact, they may wish to consider seeking out a care provider who practices optimal care, that is, the least use of medical intervention that produces the best outcomes given the woman’s individual case.
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Quote source: Menticoglou SM, Hall PF. Routine induction of labour at 41 weeks gestation: nonsensus consensus. BJOG 2002;109(5):485-91.